Rashi on Exodus 32:10/רש"י על שמות ל״ב:י׳

1הניחה לי LET ME ALONE — So far we have not heard that Moses had prayed on their behalf and yet He says “let Me alone!” which implies a refusal to his entreaty! But by saying this He opened the door to him (offered him a suggestion) intimating to him that if he prayed for them He would not destroy them (Shemot Rabbah 42:9; cf. also Berakhot 32a).